Many modern electronic devices include haptic components to provide kinesthetic feedback to a user of the device. For example, an electronic device such a cellular telephone may include a vibration motor that may vibrate for a period of time to notify a user of an incoming telephone call. Electronic devices which may benefit from haptic components include cellular telephones, smart phones, personal digital assistants, tablet computers, laptop computers, track pads, wearable devices, and peripheral input devices such as keyboards, buttons, dials and computer mice.
Further, market demand for improved electronic devices has motivated advancements in device durability, thinness, and weight. As a result, internal components such as haptic devices are expected to occupy a smaller volume. Designing a haptic device that is durable, thin, and sufficiently powerful to enable the user to perceive the intended haptic effect presents several challenges. For example, many haptic devices require a cylindrical motor to drive a mass positioned eccentrically about the motor's axis. As the cylindrical motor spins, the eccentric mass experiences asymmetric forces causing a perceivable displacement of the mass and motor within a plane tangent to the axis of rotation. With a sufficiently high number of revolutions per minute, the cylindrical motor and eccentric mass are consistently and asymmetrically displaced. If the cylindrical motor is structurally coupled to the housing of an electronic device, this displacement may be perceived as a vibration.
However, due to the limited space within portable electronic devices having reduced thickness, a cylindrical drive motor and an eccentric mass are conventionally assembled so that the shaft of the drive motor is the axis of rotation of the eccentric mass. In this manner, the eccentric mass and drive motor may occupy a smaller space within the housing of portable electronic device. However, this configuration may limit the number of positions and orientations a haptic element may take within the housing.
Moreover, as a cylindrical drive motor decreases in size it also decreases in power and torque and may not have sufficient torque to spin an eccentric mass to a speed sufficient for a user to perceive a vibration. Similarly, the eccentric mass may also decrease in size such that displacement of the mass is no longer sufficient to cause a vibration of adequate magnitude to be perceived by a user. Accordingly, the dimensions, size, and shape of electronic devices including a cylindrical drive motor and eccentric mass may be undesirably constrained by the minimum size, shape, and torque requirements of the cylindrical drive motor and eccentric mass.
In other cases, a cylindrical drive motor with an eccentric mass may be undesirable or unsuitable as a haptic feedback element. For example, a single pulse or a series of distinct pulses may be desirable to notify a user of a particular event. As a result of relatively low torque produced by a relatively small drive motor, it may not be possible for a cylindrical drive motor to spin and stop an eccentric mass with sufficient speed to product a single pulse. As a result, a cylindrical vibration motor may be limited in both minimum size and the type of haptic feedback it may provide.
Accordingly, there may be a present need for a durable, thin, and high torque haptic feedback element suitable to provide both vibration and single pulse haptic feedback.